How to run virtualbox in virtualbox for mailware isolation

[sam the vbox man]

I have been trying to run a virtualbox in another virtualbox for malware isolation but every time i get it set up i come up with the following error:

Failed to open a session for the virtual machine windows box.

VT-x is not available. (VERR_VMX_NO_VMX).

Result Code: E_FAIL (0x80004005)
Component: Console
Interface: IConsole {8ab7c520-2442-4b66-8d74-4ff1e195d2b6}

I have looked to see if i can open up the bios and change visualization to on but i couldn't find anything on this.
any help would be greatly obliged.

[Perryg]

Nested virtualization is not supported, but if you must try you need to understand that VMX is not passed to the guest so you will only be able to run 32-bit OSes.
You also need to have a host and processor that supports EPT.